BIOACCUMULATION
Bioaccumulation is the accumulation of contaminants by species in concentration that are magnitude higher than the surrounding environment.


BIOCONCENTRATION
Bioconcentration refers only to the uptake of substances into the organism from water alone. 


BIOMAGNIFICATION
Biomagnification applies to trophic levels. The buildup of substances in the bodies of organisms at higher trophic levels of food webs.


THE DIFFERENCE?
Bioconcentration and bioaccumulation occur within an organism while biomagnification occurs across trophic levels. Bioconcentration refers only to the uptake of substances into the organism from water alone while bioaccumulation is the more general term because it includes all means of uptake into the organism. Thus, we can say that bioaccumulation = bioconcentration + biomagnification.